Inter-outer telephone system and equipment



INVENTOR.

ATTORNEYS.

R. VARLEY May 18, 1937.

INTER-OUTER TELEPHONE SYSTEM AND EQUIPMENT Filed Sept. 26, 1955 4 Sheets-Sheet 1 R. VARLEY May 18, 1937.

INTER-OUTER TELEPHONE SYSTEM AND EQUIPMENT Filed Sept. 26-} 1935 4 Sheets-Sheet 2 INVENTOR. VA/GZ 5x ATTORNEYS.

May 18, 1937. R. VARLEY 2,080,586

INTER-OUTER IELEPHONE SYSTEM AND EQUIPMENT 4 Sheets-Sheet 3 Filed Sept. 26, 1935 gr gaj zam $4: 2%

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INYENTOR.

ATTORNEYS May 18, 1937. R. VARLEY 2,080,586

- INTER-OUTER TELEPHONE SYSTEM AND EQUIPMENT Filed Sept. 26, 1935 4 Sheets-Sheet 4' INVENTOR.

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w/ r/vassx 66 J W v ATTORNEYS Patented May 18, 1937 UNITED STATES PATENT OFFICE INTER-OUTER TELEPHONE SYSTEM AND EQUIPMENT Richard Varley, St. George, Staten Island, N. Y., assignor to Inter-Outer Telephone Corporation, Dover, Del., a corporation of Delaware may selectively communicate with any other 7 l station and may also be acoustically coupled to a. subscribers telephone instrument of an outside electrically independent public telephone system without interfering with the property or operation of the public telephone system, where- 20 by any station of the private inter-ofiice system is afforded the full facilities and service of the public telephone system.

Another object of my invention is to provide an inter-outer telephone system of the character 25 indicated in which the telephone operating circuits of the inter-ofiice system are connected in one suitable circuit arrangement forinter-v oflice communication and are connected in another suitable circuit arrangement when the 30 system is employed in acoustical connection with the outside or public telephone system.

A further object of my invention is to provide simple and-eifective means under the control of the users at any of the branch stations 35 of the inter-office system for readily establishing the optimum arrangement of telephone operating circuits for the class of service to be employed; for instance, with the telephone receivers and transmitters of any two communi- 40 cating stations of the inter-office system connected in multiple for interior use and with the telephone receiver and transmitter of any branch station connected in separate independently operable receiving and transmitting circuits with the respective telephone transmitter and receiver of an acoustical coupling device at the main or operators station, for acoustically communicating with the outside or public telephone system. 50 -Another object of my invention is to provide such an inter-outer telephone system with auto- 'matic interlocking of the various branch stations, in such manner that after the telephone facilities have been established for acoustically 55 coupling any branch station and the public telephone system, all other branch stations are automatically locked against interfering acoustical use, while at the same time signals are effected at all of the other branch stations to indicate that the inter-office system is in such use.

- A further object of my invention is to provide for such interlocking and signalling features as above indicated, while making provision to enable inter-ofiice communication between branch stations during the period when one branch station is being used for acoustical communication with the public telephone system.

A still further object of my invention is to provide telephone equipment, either in the form of wall or desk types of telephone sets, for inter-outer telephone service, which shall be simple and reliable in construction and operation and which shall be particularly adapted to carry out effectively the shifting or change-over of telephone circuit connections for arranging the system either for inter-office use or for outside serv- ,ice through an acoustical coupling with the public telephone system.

These and other objects of my invention and features by means of which they are accomplished will become apparent from the following description of the invention in connection with the accompanying drawings, of which Fig. 1 is a diagrammatic view of the circuit connections of an inter-outer telephone system embodying my invention, and in which the branch stations of the interior or inter-oflice system are provided with wall type telephone sets;

Fig. 2 is a diagrammatic view of the circuit connections of a modified form of my invention, in which the branch stations of the interior telephone system are provided with desk type telephone sets;

Fig. 3 is a perspective view of a desk type telephone set, such as used at the branch stations of the system illustrated in Fig. 2;

Fig. 4 is a, view, partially in section and partially in elevation, of the telephone set shown in Fig. 3, the section being taken substantially on the section line 4-4 of Fig. 3;

Fig. 5 is a view, partially in section and partially in elevation, of the telephone set shown in Fig. 3, the section being taken along the section line 55 of Fig. 3;

Fig. 6 is a fragmentary view, partially in section and partially in elevation, of the apparatus shown in Fig. 5, the'section being taken along the section line 6-6 thereof;

Fig. '7 is a fragmentary view, similar to that of Fig. 6, and showing a portion of the apparatus in another operating position;

Fig. 8 is a fragmentary view, similar to that of Fig. 5, and illustrating a portion of the apparatus in another operating position;

Fig. 9 is a perspective view of a slidable interlocking plate constituting a part of the telephone set shown in Fig. 3;

Fig. 10 is a bottom plan view of the slidable interlocking plate and other associated parts cooperating therewith;

Fig. 11 is a fragmentary sectional view of a portion of the apparatus including a signal button, and

Fig. 12 is a plan view of an auxiliary switching device forming a part of the telephone set shown in Fig. 3.

Referring now to Fig. 1 of the drawings, which illustrates my invention as applied to the use of wall type telephone sets at the branch stations of the inter-oflice system, the invention comprises a main or operators station 0 and a plurality of branch stations A and B, which are 10- "T cated at separate points and are provided with suitable telephone equipment and communicating connections to enable selective telephonic communication between any two branch stations. The several stations of the inter-office system are also provided with a suitable interconnecting signal system S whereby any station may signal any other station of the system. The operators station 0 is also provided with a subscribers telephone instrument T of an outside or public telephone system and an acoustical coupling device C disposed adjacent thereto and adapted for use in effecting an acoustical coupling between the public telephone system and any of the branch stations of the interior telephone system.

The public telephone set T comprises a base 2, a dial operating mechanism 4, and a cradle 6 upon which a French style telephone instrument F is adapted to rest when not in use. The telephone instrument'F is of well-known constructionand embodies a receiver 8 and a transmitter III which are disposed in fixed spaced relation at the respective ends of a hand grip l2. For the purpose of signalling the operator, whenever the telephone instrument F is in use and out of its cradle, the base 2 of the telephone set is normally positioned upon a floating platform I4 of a sub-base I6 within which the platform is disposed and mounted upon aplurality of supporting springs 18. Attached to the bottom of the floating platform l4 by means of an insulating block 20, is a spring contact 22, and another spring contact 24 is mounted upon an insulating block 25 secured to the sub-base I3. The spring contacts 22 and 24 are positioned in vertical relation so that an electrical engagement thereof may be efiected whenever the floating platform l4 and associated spring contact 22 are permitted to be raised in position.

Under normal conditions when the telephone instrument rests in its cradle, the weight of the entire telephone set is sumcient to depress the floating platform I4 against the action of the springs l8 so that the spring contacts 22 and 24 are held out of engagement. However, when the telephone instrument F is picked up for use, the weight of the base 2 is insufllcient to hold the platform i4 and associated spring contact 22 in their lowered positions against the action of the springs l8, which raise the platform and bring the spring contact 22 into electrical engagement with spring contact 24. In this way a circuit is established from a source of energy marked AC through a visible or audible signal device 26 which immediately becomes operative to warn the operator that the telephone instrument F must be restored to its cradle as soon as the telephone conversation has terminated. The circuit for the signal device 26 includes conductor 28 from one side of the source of power, spring contact 22, spring contact 24, conductor 30, signal device 28, conductor 32 and conductor 34 to the other side of the source of power. Another important function in the operation of my invention is also carried out by the spring contacts 22 and 24, as will later be described.

The acoustical coupling device C is located at the operators station 0 a convenient distance from the public telephone set T so as to permit the French telephone instrument F to be temporarily placed in acoustical operating relation with the coupling device C whenever the inter-ofllce system is operatively connected to the public telephone system. The coupling device C comprises a cabinet of which only a portion of a front inclined panel 38 is illustrated. This panel is provided with a plurality of openings 38 and 48 disposed in substantial vertical alignment and spaced apart a distance correspond ing to the spacing of the receiver 8 and transmitter ill of the French type telephone instrument F, so that the telephone instrument may be placed on the front panel of the coupling device C with its receiver and transmitter in registry with the upper and lower panel openings 38 and 40, respectively. In this position the instrument F is adapted to be suspended or supported by means of an outwardly extending supporting flange 42 which is preferably semicircular in form and which engages the receiver end of the instrument.

Immediately behind the upper panel opening 38 and in registry therewith is mounted a microphone 44 which is preferably of the well-known two-button type, although other types may be used. In a corresponding position behind the lower panel opening 48 is a loud-speaker 46 of any suitable and well-known construction. When the French telephone instrument F occupies its operative position on the coupling device, the sound waves emanating from the receiver 8 are picked up acoustically by the microphone 44 for transmission to the interior or inter-oflice telephone system, while the sound waves originating at a branch station of the inter-office system and emanating from the loudspeaker 46 are acoustically picked up by the transmitter ID of the French telephone instrument and thus delivered to the public telephone system.

For certain desirable control or signal purposes, the couplingflevice C is also provided with a control switch A8 having a stationary contact 50, a cooperating movable switch arm. 52 and an actu ating rod 54 which projects through the front panel 3 and is provided with a. button or head 58. This actuating rod 54 is located intermediate the panel openings 38 and 40 and in line therewith so that in order to eifect a full and emcient acoustical coupling between the French telephone instru-' ment F and the coupling device C, it is necessary for the actuating rod 54 of the control switch 48 to be depressed by the operator before the instru ment can be placed in operative position.

Also associated with the coupling device C and conveniently disposed within its cabinet is molectronic sound amplifier 60 of conventional construction, including vacuum tubes of the amplifying and rectifying type, choke coils, transformers, condensers and other elements commonly employed in the construction of such' devices. A suitable amplifier is typified by the RCA Victor portable sound amplifier-Type P. G.63, or the Universal amplifier assembly (6 watts) may be employed. Whilethe particularamplifiers mentioned are adapted to be connected to an alternating current source of power, my invention may be carried out with any type of electronic amplifier such, for example, as those which are connected to a direct current source of power or those which are operated on batteries. All such amplifiers, regardless of their type, are provided with means for regulating or adjusting the degree of amplification. This is a desirable adjunct in my system, but since it is common with all types of amplifiers, it is typified in the drawings only by a simple adjusting knob 62. The amplifier 60 is connected to the microphone 44 by means of input conductors 64 and is provided with power terminals 66 and output terminals 68, as is common practice.

The cabinet of the coupling device C also contains auxiliary devices, such as an electromagnetic relay switch 10, a signal device or buzzer I2, batteries 14 and 16, as well as the control switch 48 and certain necessary circuit connections for the system.

Also located at the main or operators station and constituting a part of the inter-oflice telephone system, is an ordinary wall type telephone set comprising a transmitter 80 and a receiver 82 which may, if desired, comprise parts of a single hand-grip telephone instrument, although, as shown diagrammatically in the drawings, this transmitter and receiver are separate pieces of equipment. The receiver 82, when not in use, is hung on the free hooked end of a hook lever 84 which is pivotally mounted at 86 and normally rests against a stop 88 when the receiver 82 is hung up. The hook lever 84 is provided with an insulating button or finger 90 which is adapted to engage and actuate a spring contact 92 into engagement with a cooperating spring contact 94 when the hooklever 84 is raised in position by a spring 86 whenever the receiver 82 is picked up for use.

The branch stations A and B are alike, and, as illustrated, each embodies a wall type of telephone set, although my invention in some of its aspects is not so restricted. The telephone set at station A, which is similar to that at the other branch stations, comprises a transmitter I00, a receiver I02, a hook lever I04, a manually operable shift lever I06, a control or change-over switch I08 and a latching and signalling mechanism IIO.

As stated in connection with the telephone set at station 0, the transmitter I 00 and receiver I02 at branch station A and B may constitute parts of a single hand-grip instrument, if so desired, but are illustrated as separate units. The receiver I02 is provided with an upwardly extending supporting member II2 having an opening II4 therein. The receiver I02, when not in use, is hung by means of the supporting member II2 upon the free end of the hook lever I04 which is pivotally mounted at I I8 and is in the form of a bell-crank brought into electrical engagement when the receiver I02 is removed from the hook lever and said lever is raised by the spring I22 into the position shown in dotted lines.

The control or change-over switch I08 comprises a plurality of spring contacts a, b, c, d, e, f, g, h, i, 7', k, l, m, which are mounted in spaced relation upon an insulating block I30, and some of which are backed by relatively rigid strips or members I32 for limiting the degree of flexure of their associated spring contacts and thus preventing accidental engagement with adjacent spring contacts. In order to facilitate the operation of the change-over switch I 08, the spring contacts b and k are somewhat extended, while other spring contacts e and h are still further extended, the latter being provided with insulating fingers or buttons I34 which are adapted to engage and operate the spring contacts b and k respectively in certain positions of the changeover switch.

The actuation of the change-over switch I08 is effected by the manually operable shift lever I06,

the operation of which is dependent upon the intended character of use of the system, that is, whether it is to be used for inter-oflice communication or whether for acoustical connection of one of the branch stations with the public telephone system. The shift lever I06 is pivotally mounted at I36 to move in the same vertical-plane as the hook lever I04. The free end thereof is in the general form of a letter T and embodies an integral upwardly projecting segment I38 and a downwardly projecting arm I40 which carries a roller I44. The shift lever I06 normally occupies the position shown in full lines in Fig. 1 and is normally .biased to that position by means of spring I42, which spring also serves to bias the shift lever I 06 to its other and lower operating position as shown in dotted lines when it is manually moved across its dead center position.

In transverse section the outer end of shift lever I06 is of U shape, with the open end of the U at the bottom, so that when it is moved by the user to its lower operating position it straddles, but does notengage, the hook lever I04, even when the latter occupies its raised position. By reason of this cooperative arrangement and location of the shift lever I06 and the hook lever I04, together with the fact that the upper end of the receiver suspension member II2 extends considerably above the point of support thereof, it becomes necessary for the user in restoring the receiver I 02 to its hanging position on the hook lever to preliminarily raise the shift lever I06 to its upper operating position.

In order to actuate the change-over switch I08 by the shift leverv I06, the roller I44 carried by the arm I40 of said lever is positioned intermediate the extended spring contacts e and h, and in the upper operative position of the shift lever I06, the roller I44 engages spring contact e and thereby causes an electrical engagement to be effected between spring; contacts d and e, while by reason of the'engagement of the insulatin button I34 carried by spring contact e, an electrical engagement is also eifected between spring contacts b and a. The'construction of the control switch I08 is such that when the shift lever I06 occupies its upper position, spring contacts 0, f, i, l and m occupy positions in which no electrical engagement with other spring contacts is effected, while electrical engagements between spring contacts a and h and between 7' and k are established, as indicated in Fig. 1, in addition to those already set forth. I

The positions just described of the various spring contacts is that which they occupy when the change-over switch I08 is adapted for interofiice communication, under which conditions the shift lever I06 occupies its raised position, as shown in the drawings. y

In order to arrange the change-over switch I08 for communication between a branch station and the public telephone system through the agency of my acoustic coupling device C, the shift lever I06 is manually moved to its lower position. During this movement, the roller I44 carried at the end of the shift lever arm I40 is moved to the right to permit spring contacts b and e to assume their normal natural positions inwhich they establish electrical connections with spring contacts 0 and 1, respectively. Furthermore, the roller I44 engages the upper extended end of spring contact h and forces it to the right to disengage spring contact 9 and establish an electrical engagement with spring contact 2. Concurrently therewith the insulating button I34, carried by spring contact h, is brought into engagement with the extended end of spring contact k, which is thereby forced to the right to disengage spring contact 7' and to establish electrical engagement with spring contacts 1 and 111.. Under these conditions spring contacts a, d, g and 7' occupy positions in which no electrical engagement with any of the other spring contacts is effected. I

For the purpose of preventing inter-outer operation of other branch stations when one of the branch stations is being utilized for communication with the public telephone system, each of the branch stations is provided with a latching and signalling mechanism IIO which includes theppwardly projecting segment I38 having a notch I46 therein, into which a locking finger I46 of a pivotally mounted armature-latch member I50 may be positioned under certain circumstances in order to lock the shift lever I06 against being moved into its lower position. This pivotally mounted armature-latching member I50 constitutes an armature of an electromagnet I52 and is nomially held in its upward position against a stop I54 by means of a spring I56. When the electromagnet is energized the locking finger I48 of the armature latch member I50 is pulled down into the notch I46 into locking engagement with the segment I38, provided that the shift lever I06 occupies its upper position, whereby the movement of the shift lever to its lower position is prevented. Of course, if the shift lever I06 occupies its lower position it will be impossible for the locking finger I48 to effect a locking engagement with the notch I46.

Disposed above the armature-latch member I50, and in the path of movement thereof, is a bell-crank lever I58 which is pivoted at I60, and its horizontal arm carries an adjustable weight I62, while the upper extremity of its upwardly extending arm carries a signal disk I64.. The bell-crank lever I58 constitutes a sort of semaphore signal, and normally occupies a position such as shown in the drawings with a depending finger I66 thereof resting upon the armaturelatch member I50. However, when the electromagnet I52 is energized and its armature I50 is pulled down into locking position, the bell-crank semaphore I58 rotates in a counterclockwise direction by reason of the weight I62 and moves the signal disk I84 into registry with an opening or window I68 in the casing (not shown) of the telephone wall set. If the signal disk I64 be painted red for convenience, it will visibly indicate through the window I68 that the inter-oflice system is already busy" or in use. Any party desiring to use the branch station will therefore wait until the system is clear or out of use. Of course, in lieu of a semaphore signal any other suitable visible or audible signal may be employed.

For the purpose of enabling the operator at station 0 to selectively signal any branch station, such as A or B, and also for any branch station to signal the operator's station or any other branch station, a suitable buzzer or signal system S is employed, and associated therewith, are suitably located push buttons and buzzers functioning in the usual manner. The buzzer or signal system S is common in the art and will be understood without detailed description. The system includes a battery I10 and a plurality of push buttons I12 and I12 located at the operators station, push buttons I14 and I14 located at station A and push buttons I16' and I16 located at station B, which are adapted when pressed to complete suitable circuit connections to selectively energize a plurality of signal buzzers I18 I18** and I18 respectively located at the operator's station 0 and the branch stations A and B.

Having described the general construction and operation of various parts of the system illustrated in Fig. 1, the operation thereof will now be set forth.

Assuming that the operator at station 0 desires to speak with a party at branch station A, the operator first depresses push button I12 whereby, through the agency of the battery I10 and suitable circuit connections, the buzzer I18 at station A is operated. Having signalled station A the operator, or course, removes the receiver 82 from its hook lever 84 and, as soon as the party at station A hears the call, the latter similarly removes the receiver I02 from its hook lever I04, the shift lever I06 at station A being left in its normal upper position, as shown in the drawings. The removal of the receivers 82 and I02 from their respective hook levers permits said hook levers to be raised by their respective springs, hook lever 84 at the operator's station 0 effecting the electrical engagement of spring contacts 92 and 84, and the hook lever I04 at station A causing an electrical engagement of spring contacts I26 and I28.

Under these conditions, a telephone circuit is established between stations 0 and A in which the receivers 82 and I02 and the transmitters and I00, are connected in multiple circuit for inter-office communicating purposes. This circuit is from one side of the battery I10 through conductor I80, impedance coil I82 and conductor I84 to.a junction point I66 where the circuit divides, one branch including conductor I88 which constitutes one of the interconnecting conductors between stations 0 and A, the balance of which circuit will presently be described, and the other branch including conductor I80 to another junction point I82, where the circuit again divides, one branch including conductor I84, receiver 82 at station 0, and conductor I86, while the other branch includes the transmitter 80 at station 0 and then joins conductor I86, the circuit being completed through spring contacts 84 and 82, conductor I98 and conductor 280 to the other side of the bettery. In this way, the

transmitter 80 and the receiver 82 at station 0 are connected in multiple across the battery.

Reverting now to the interconnecting conductor I88, the balance of the circuit includes conductor 202 to a junction point 204, where the circuit again divides, one branch including spring contacts d and e of change-over switch I08 at station A, conductor 206, receiver I02 at station A, conductor 208, spring contacts I) and a of change-over switch I08 and conductor 209, and the other branch including conductor 2I0, springs contacts a and k: of change-over switch I 08, conductor 2I2, transmitter I00 at station A, conductor 2, spring contacts h and g of change-over switch I08 and conductor 2I6 which joins conductor 209, the circuit being completed through conductor 2I8, spring contacts I20 and I28, conductor 220 and conductor 200 to the other side of the battery. The part of the circuit just described with respect to the apparatus at station A connects the transmitter I 00 and the receiver I02 at sai'd station in multiple across the battery I10, and also in multiple with the transmitter 80 and receiver 82 atthe operators station 0.

Upon the establishment of the telephone circuits just recited, the parties at the operators station 0 and the branch station A may converse at will. At the end of such telephonic communication, the receivers 82 and I02 at stationsv O and A are again hung upon their respective hook levers. If during the conversation the party at station A desires to hear the conversation over a loud speaker, instead of using the receiver I02, he merely depresses a button I02 associated with said receiver, which by means of an ordinary three-point switch (not shown) suitably located within the receiver casing, connects a loud speaker 222 into circuit in lieu of the receiver I02.

As already stated, any branch station may communicate with any other branch station as, for instance, station A may talk with station B. In this case the party at station A depresses push 7 button IH and thus operates the buzzer I 18 at station B. Subsequently, as the receivers I02 at stations A and B are removed from their respective hook levers, suitable telephone circuits are established in much the same manner already described and in accordance with which the receivers I02 and transmitters I00 of both stations A and B are connected in multiple across the battery I10. Inasmuch as the circuit connections of the change-over switch I08 at station B are the same as those set up by the change-over switch I08 at station A, and which have just been specifically described, it is deemed unnecessary to trace these circuits in detail, and they will be readily understood from the foregoing description.

Having described the method of operation of the inter-oflice system, I will nowexplain the mode or acoustically connecting the public telephone set T of the public telephone system with the source of power marked A. C. is connected across the signal device 26 in the manner already explained.

At the same time, the power terminals 68 of the electronic amplifier 80 are connected in parallel with the signal device 28 across the source of energy A. C. by means of conductors 224 and 226. The amplifier 00 is thereby immediately energized and the amplifier tubes are promptly subjected to heating current in order that they may be brought up to operating condition quickly so that the amplifier will be in readiness for service by the time the desired party has been called to the proper branch station.

The operator having ascertained the party desired depresses one of the push buttons, for instance push button I12 in the event that the desired party is located at station A, thereby operating the buzzer I18 The operator then picks up the receiver 82 at station 0 of the inter-office system, and as soon as the party at branch station A picks up the receiver I 02 at said station, an inter-ofilce telephone circuit, identical with that previously described, is established. The operator then informs the party at station A of the outside call, whereupon the party at station A pulls down the shift lever I06 in order to cause the change-over switch I08 to be arranged for communication with the public telephone system.

The operator then hangs up the receiver 82 of the inter-office system and, having depressed the switch-actuating rod 54 to cause electrical engagement of the switch arm 52 with the stationary contact 50, places the French telephone instrument F in acoustical relation with the acoustical coupling device C, in the manner previously described. Under these conditions, the system is arranged and in readiness for telephonic communication between station A and the public telephone system through the agency of the acoustical coupling device C, the receiver I02 of station A being connected in a receiving circuit with the amplifier 80 and the microphone 44 of the coupling device and the transmitter I00 of station A being connected in. a separate and independently operable transmitting circuit with the loud speaker 46 of the acoustical coupling device.

The establishment of these independently operable receiving and transmitting telephone circuits is effected as follows. When the shiftlever I06 is pulled down to a position shown in dotted lines in Fig. 1, the change-over switch I08 is actuated in the manner previously described to set up the necessary telephone circuit connections. The receiving circuit, starting with one of the output terminals 68 of the amplifier 60, includes conductor 228, conductor 230, spring contact c and spring contact b of change-over switch I08, conductor 208, receiver I02 at station A, conductor 208, spring contacts e and f of the changeover switch I08, conductor 232 and conductor 234 to the other output terminal 68 of the electronic amplifier 60. The transmitting circuit above referred to starts from one side of battery 14 and includes conductor 236, loud speaker 46 of the coupling device C, conductor 238, conductor 240, spring contacts 1' and h of change-over switch I08 at station A, conductor 2| 4, transmitter I00 at station A, conductor 2I2, spring contacts is and l of the change-over switch, conductor 242 and conductor 2 to the other side of the battery I4.

Accordingly, these independently operable receiving and transmitting telephone circuits are ready for use and the conversation between the party on the public telephone system and the party at station A may be carried on in the usual manner, with the messages emanating from the receiver 8 of the telephone instrument F being acoustically picked up by the microphone 44, and after being amplified to the desired controllable degree by the amplifier 60-, are transmitted to the receiver I02 at station A. On the other hand, the messages originating in the transmitter I00- of station A are delivered acoustically by the loud speaker 46 to the transmitter I0 of the telephone instrument F and are thus relayed to the party calling on the public telephone system.

Returning now to the time the shift lever I06 was pulled down to cause the change-over switch I08 to establish the necessary connections for the outside call, an important control circuit is immediately established which carries out an important function in the automatic interlocking feature already referred to, as well as in connection with the subsequent operation of the signal buzzer I2 associated with the coupling device C. It has already been set forth that the spring contact is of the change-over switch I08 is actuated by the shift lever I 06 into engagement with spring contact I. At the same time, the spring contact is also engages spring contact m from which a control circuit is completed through conductor 246, conductor 248, electromagnet I52 at station A, conductor 250, electromagnet I52 at station B, conductor 252, electromagnet 254 of the electromagnetically operated control switch I0 associated with coupling device C and thence through battery I6 to the other side of the battery I4.

By thus energizing the electromagnets I52 of the respective branch stations A and B, a downward pull is exerted upon all of their associated armature-latch members I50, all of which, except that at station A, are pulled downwardly against the action of the springs I56 whereby the locking fingers I48 thereof are positioned in the notches I46 of the respective segments I38 which constitute integral parts of the respective shift levers I06. By reason of this locking engagement, the shift lever I06 at station E and any other branch stations, except, of course, that at station A, are positively locked against manual operation and, therefore, can not be moved to their lower operating positions, until the telephone conversation between the party at station A and the party on the public telephone system is completed. Of course, in view of the fact that the shift lever I06 at station A has already been moved into its lower operating position, the latching member I50 of station A is prevented from being pulled downwardly by its associated electromagnet I52 into the notch I46 of the associated segment I38.

However, all of the other branch stations are locked against use for outside calls, as already described. Moreover, the semaphore signal devices at these other branch stations are operated, as already described, to visibly indicate at the openings or windows I68 of the respective tele phone wall sets that the system is busy for the time being. Therefore, any party at these other branch stations, noting that the busy signal is set, will refrain from attempting to utilize the system for outside use until this visible signal indicates that the system is clear and ready for use.

At the same time that the automatic locking and signalling system just described is rendered operative, the electromagnet 254 of the control switch I0 at the operators station is also energized, and this magnet attacts ,its armatureswitch arm 256 against the action of a spring 258. Thereby, the cooperating contact members 260 associated therewith are disengaged to interrupt the energizing circuit of the signal buzzer I2, which is also in circuit with the switch arm 52 and stationary contact 50 of the control switch 48, which were engaged by the actuating rod 54 at the time that the telephone instrument F was placed in acoustical position with the couplingdevice 0. Under these conditions, of course, the buzzer I2 is open-circuited and therefore prevented from operating for the time being.

When the telephone conversation has been completed, the party at station A hangs up the receiver I02. By reason of the fact that the receiver-supporting member II2, from which the receiver I02 is suspended, is provided with an extended upper end, it is necessary that the shift lever I06 at station A be moved by the user to its upper initial position before the telephone receiver I02 can be hung upon the hook lever I04.

In so moving the shift lever I06 to its upper position, the various spring contacts of the changeover switch I08 assume their original positions to reestablish their proper circuit connections for inter-oflice communication, as will be understood. During this shift of connections of the changeover switch I08, the spring contact m is disengaged by the spring contact In, thereby interrupting the control circuit through the energizing windings of the interlocking electro-magnets I52 at the various branch stations, as well as through the energizing winding of the electromagnet 254 of the control switch I0 in the coupling device. Thereupon, the springs I56 of the several armature-latch members I50 at the various'branch stations operate to raise the latch members, and at the same time to move the respective semaphore signal devices I64 to their initial inoperative positioris to indicate that the system is clear and ready for subsequent use.

Upon the deenergization of the electromagnet 254, the armature-switch member 256 thereof is restored by the spring 250 to its original position in which the cooperating contact members 260 are brought into electrical engagement. This complates a circuit from one side of battery 14 through conductor 236, stationary contact 50, switch arm 52, conductor 262, buzzer I2, switch arm 256, cooperating contacts 260 and conductor 264 to the other side of the battery. Immediately thereupon, the buzzer I2 is operatedto warn the operator at station 0 that the conversation has been terminated and that the French'teiephone instrument F should be returned to its cradle on the public telephone set T. This buzzer I2 continues to operate until this has been done. In restoring the telephone instrument F to its cradle, the operator pulls out the actuating rod 54 of the control switch 48 and thus interrupts the buzzer circuit and restores the coupling device C to normal condition in which it is in readiness for further use.

The energization of the electronic amplifier 60 is, of course, interrupted as soon as the telephone instrument F again rests on its cradle, by reason of the fact that the total weight of the telephone set T is then sufficient to depress the floating platform and disengage the cooperating spring contacts 22 and 24. Obviously, the signal device 26 is also rendered inoperative at the same time.

The combined inter-outer telephone system of my invention is thus in readiness for future use, either in inter-oillce communication or communication with the outside or public telephone system through the agency of the acoustical coupling device C.

While I have described in detail the operation of my improved inter-outer telephone system in connection with receiving a call from a party on the public telephone system for a party at one of the branch stations of the inter-ofilce system, it will be understood without further explanation that a call may originate at any of the inter-office branch stations.

I wish to point out that, although during telephone communication between any one branch station and the public telephone system, the shift levers I06 for actuating the change-over switches I08 at all other branch stations are locked against interfering use and busy signals are displayed to indicate that the system is being used for interouter communication, it is still possible for the operator at station and parties at all other branch stations, except the one in use, to communicate through the inter-office system with any of the other branch stations.

Reference may now be had to Fig. 2 of the drawings which illustrates a modified form of my invention in which desk-type telephone sets are employed at the several branch stations of the system in lieu of telephone sets of the wall type, but which otherwise operates inthe main along similar lines to that previously described in connection with Fig. 1. Preliminary to an explanation of the operation of this system, a description of my improved desk-type of telephone set will first be given.

Therefore, referring to the structural views of Figs. 3 to 12, inclusive, and more specially to Fig. 3, each of the branch station desk-type telephone sets D embodies a base or casing 266 having a cradle 26'! upon which rests a French type of telephone instrument E comprising a receiver 268 and a transmitter 210. The base 266 is provided with a plurality of signal or push buttons, such as I14 and I14 depending on the number of branch stations employed in the system, together with a shift button I06 for operating a modified type of change-over switch I08 (Fig. 6) which is disposed within the casing.

The telephone cradle 261 is yieldingly mounted, as shown in Fig. 4, upon the top of a T-shaped supporting pedestal 212, the lower end of which is provided with a threaded projection 214 that is screwed into a threaded opening in the top of the base member 266 and is secured in position by means of a lock nut 218,. pedestal 212 has a central opening therein, through which a supporting rod 280 extends and is adapted for vertical movement with respect thereto. When the telephone instrument E is removed, the cradle 261, together with the supporting rod 280, is normally held in its uppermost position by means of a plurality of coil springs 284 which respectively surround rods or pins 286 that are threaded into the top of the base 266. The lower ends of the pins 286 are provided with nuts 288 upon which rests a cross member or strip 280. The coilsprings 284 are supported at their lower ends by the cross strip 290 and another cross strip 292 rests upon the upper ends thereof. The strip 292 is suitably secured, as by welding, to a collar 284 which This supporting surrounds the cradle supporting rod 280 and is fastened thereto by set screw 286 (Fig. in such a position that the springs 284 are placed under sufficient compression to raise the supporting rod 280 and associated cradle 26'! to their uppermost positions when the telephone instrument E is removed therefrom, while permitting the springs to be compressed to a certain degree when the' telephone instrument E rests upon the cradle.

The movement of the cradle 26'! and its supporting rod 280 is utilized to control the operation of a switch 300 comprising a plurality of spring contacts 302 and 304 (Figs. 4 and 12) which are adapted to be connected in one of the telephone circuits, as will later appear. The spring contacts 302 and 304 are insulated from one another and are mounted on an upwardly turned lug 306 of the bottom cross strip 290. These spring contacts 302 and 304 are normally engaged when the telephone instrument E is removed from its cradle, but when it rests thereon, the weight upon the cradle is suflicient to compress the springs 284 andeffect the disengagement of the spring contacts by means of a roller 308 which is carried by a supporting member 3|0 that surrounds the rod position such that it disengages the spring contact 302, which permits said contact to establish an electrical engagement with its cooperating contact 304. The change-over switch I08 (Fig. 6) is mounted within the casing 266 and below the inclined top panel 3 thereof, and comprises two oppositely disposed groups of spring contacts I and 1]. group 3: comprising a plurality of spring contacts a, b, c, d, e and f and group 11 comprising a plurality of spring contacts g, h, i, 7", k and l. The spring contacts constituting the group a: are mounted in an insulating block 3|6 which is secured by threaded bolts 3m to a supporting strip 320. The strip 320 is carried at the lower ends of a plurality of tubularsupporting rods 322 which are suitably fastened by means of threaded bolts 323 to a plate 324. The plate 324, in turn, is suitably secured to the underside of the inclined top panel 3 'of the base 266. Similarly,

the spring contacts comprising the group y'are rods 328 that are also suitably secured by threaded bolts 328 to the plate 324. v

For the purpose of obtaining concurrent actuation of certain of the spring contacts of both groups a: and 1!, spring contacts b, e, h and k are provided with bifurcated extended ends which project into suitably spaced circular grooves b". c", h" and 7:" (Fig. 8) that are provided in a floating cylindrical member 330 of insulating material. In this way, the respective groups a: and y of spring contacts constituting the change-over switch I08 are mechanically interconnected by means of the floating cylindrical member 330.

The normal positions of the respective spring contacts of the change-over switch I08 are shown in Fig. 6, from which it will be seen that electrical engagement is effected between the following pairs of spring contacts, a and b, d and e, a

and h, and a" and k. The remainingspring contacts c, f, 2" and Z are so positioned as not to have electrical engagement with any other of said spring contacts. Adjacent the several spring contacts, constituting the change-over switch III, are a plurality of substantially rigid backing strips 332 for limiting the fiexure of the spring contacts in order to prevent accidental engagement with the other spring contacts in proximity thereto.

The component spring contacts of the changeover switch I08 are also adapted to occupy another operating position, as shown in Fig. 7, and the actuation thereof into such position is effected by means of the shift button I06 which projects upwardly through the inclined top panel 3I4 of the casing 266, and is disposed in vertical alignment with the floating member 330. The head of the shift button I06 is preferably .composed of insulating material and is secured to an actuating rod 334 of conducting material which is pro-. vided at its lower end with a cone-shaped head 336 constituting a cam member and provided with an upper shoulder 338.

The shift button I06 is slidably mounted in vertically disposed openings 340 and 342 respectively provided in the top panel 3 of the casing and in a plate or block 344 of insulating material. The insulating block 344 is rigidly mounted by means of tubular supporting members 346 to the plate 324 in a suitable manner, and secured to the bottom of the insulating block 344 is a U-shaped strip 348 of conducting spring material, such as brass, for example. This conducting spring strip 348 is provided with a bifurcated free end 348' which straddles the upper end of the actuating rod 334 in such manner as to have an electrical engagement therewith while at the same time biasing the shift lever I06 to its uppermost position, as shown in Fig. 6. A terminal member 350 adapted for an external electrical connection is secured to the insulating block 344 in electrical engagement with the lower end of the spring strip 348.

Before describing the manner in which an electric circuit is completed through the spring 348. rod 334 and conical head 336, the mode of operation of the change-over switch I08 by means of the shift button I06 will be set forth.

Assuming the shift button I06 to occupy its initial position, as shown in Figs. 5 and 6, in which the change-over switch I08 is positioned as already described and illustrated in Fig. 6, in order to actuate the change-over switch I08 to its other operating position, as shown'in Fig. 7, the user merely depresses the shift button I08 against the action of the spring 348. The lower end of the conical head 336 thereupon engages the upper end of the cylindrical floating member 330 of insulating material which is forced downwardly in opposition to the spring action of the spring contacts b, e'., h and k which are mechanically associated with said insulating floating member 330.

Latching mechanism M is provided for retainfrom spring contact d and an electrical engagement with spring contact I is established. Moreover, spring contact h is moved out of engagement with spring contact 9' and into electrical engagement with spring contact 1', while spring contact k disengages spring contact 7" and establishes an electrical engagement with spring contact I. In the depressed position of the shift button I06 spring contacts a, d, g and 7" are left in such positions that they are out of electrical engagement with any other of the spring contacts.

The latching mechanism M, previously referred to, comprises a fixed plate 352 and a slidable latching plate 354 which carries a roller 356 at its right hand end, as viewed in Figs. 5, 8 and 9 and which is urged or biased to the right by means of an adjustable spring 358 so that it tends to maintain the roller 356 in the path of movement of a conically shaped cam or collar member 360 which is fixed by means of a set screw 362 (Fig. 5) to the supporting rod 280 upon which the cradle 261. is mounted. More specifically, the fixed plate 352 is positioned below and spaced apart from the insulating block 344 'by means of tubular supporting members 364 which are interposed between the fixed plate 352 and the insulating block 344 and suitably secured to both members. This fixed plate 352 is provided with an opening 366, shown in Figs. 6, '7 and 11, disposed immediately below the conicaliy shaped head 336 of the shift button rod 334, in order to permit the downward movement thereof. The slidable plate 354 is positioned below and in spaced relation to the fixed plate 352 and is supported upon guide members or screws 310 which are screwed into the fixed plate 352. These guide screws 310 pass through longitudinally disposed slots 312, best shown in Figs. 9 and 10, in the slidable plate 354 and permit of longitudinal movement thereof. An opening 314 is also provided in the slidable plate 354 in slightly oii'set registry with the opening 366 in the fixed plate 352 and through which the conical head 336 of the shift button I06 may pass when said button is depressed to actuate thespring contacts of the change-over switch I08.

In order that the slidable latching plate 354 may be biased to its right hand position by means of the spring 358, said plate is provided with an elongated centrally located slot 316 (Figs. 5, 9 and 10) through which projects a cylindrical stud 318 which is suitably secured to the'fixed plate 352 and is provided at its lower end with a set screw 380 by means of which an adjustable pin 382, which passes through an opening in the stud 318, may be securely fastened in position. The inner end of this pin 382 is secured to one end of the biasing spring 358, while the other end of said spring is secured to a pin 304 which is fixedly mounted to the slidable plate 354 and projects downwardly therefrom. By suitably positioning the adjustable pin 382 the tension of the biasing spring 358 may be regulated, as desired, in order to actuate the slidable plate 354 to the right, as viewed'in Figs. 5 and 8, until an adjustable limit stop, comprising a set screw 388, which is carried by a supporting bracket 3" suitably attached to the slidable plate 354, is brought into engagement with the end of the insulating block 344.

The roller 356, previously mentioned, is carried upon a bifurcated bracket member 390 that is secured by screws 382 to the right hand end (Figs. 5 and 9) of the slidable plate 354.

When the change-over switch I08 is actuatedlinto the position shown in Fig. '7 by depressing the shift button I06, the conicalhead 336 at the lower end of the shift button rod 342 engages one side of the opening 314 (Fig. 8) 'in the slidable plate 354 and, by reason of the cam action, of the conical head 366, forces it to the left, as viewed in Figs. 5 and 8, to a slight degree until the shoulder 338 of said head passes below the slidable plate. Thereupon, the biasing spring 358 forces the plate to the right to cause it to slip in back of the shoulder 338 and thereby latch the shift button I06 in its lowered or depressed position, as shown particularly in Fig. 8.

In this position, not only is the shift button I06 latched against the action of the spring strip 348, but the insulating cylindrical floating memher 330 is also held in its lowered position, where- 354 occupy their right hand positions, as indicated in Figs. 5 and 8. However, when the French telephone instrument E is restored to its cradle, the Weight thereof is suflicient to depress the supporting rod 280 and the cam member 360, which latter forces the roller 356 and the associ-' ated slidable latching plate 354 to the left to disengage said plate from the conical head 336 of the shift button I06. Thereupon, the spring strip 348 raises the shift button I06 to its upper position, thus permitting the various spring confacts of the change-over switch I08 to resume their normal positions, as shown in Fig. 6, while at the same time interrupting the electrical engagement of the slidable plate 354 with the conical head 336 of the shift button.

By reason of the construction just described, it becomes unnecessary for the user to hold the shift button I06 in depressed position, as it is latched in such position by the slidable plate 354 at the time it is initially depressed. It remains so latched until the telephone instrument is restored to its cradle, when the shift button I06 and the change-over switch I08 are automatically released and returned to their initial positions.

For the purpose of preventing the operation of the change-over switch I08 under certain conditions of the system in which the desk-type telephone set D is being utilized, an electromagnetically operated locking device 390, which comprises an electromagnet 388 and a pivotally mounted armature 400, is disposed beneath the cylindrical floating member 330, as best viewed in Fig. 5. Normally, the armature 400 is held in the position shown against an. adjustable stop 402 which is carried by a bracket 404, between which and the armature 400 a retracting spring 406 is secured. In its normal position when the electrcmagnet .398 is deenergized, the armature 400 is disposed beyond the path of movement of the floating cylindrical member 330 of changeover switch I08. Under these conditions, the change-over switch may be actuated by the shift button I06. However, if the circuit connections of the system in,which the telephone setD is employed are such as to energize the magnet 398, its armature 400 is drawn to the left (Fig. 5) into such position that the upper end thereof is in the path of movement of the floating member 330 and thus prevents the actuationof the changeover switch I08.

Referring now more particularly to Figs. 5 and 11, the signal push buttons I14 and II4', which comprise insulating material, are slidably mounted in openings in the inclined top panel 3 I 4 of the casing 266 and each is provided with a downwardly projecting rod 408 which projects through an opening M0 in the insulating block 344 and is provided at its lower end with a nut M2. The signal button is normally held in its uppermost position by means of a U-shaped spring strip 4I4 of brass or other conducting material, the lower end of which is suitably secured to the insulating block 344 and the upper end 4I4 of which is bifurcated and straddles the rod 408 beneath the insulating portion of the push button.

In order to permit of depressing the signal buttons, openings 5, Figs. 8 and 11, are provided in the fixed plate 352 immediately below the nuts 4I2, while further and somewhat larger openings 4 I 8 are provided in the slidable latching plate 354 for the same purpose. When the push buttons are depressed by the user, as shown in Fig. 11, the free ends 4I4' of the spring strips 4I4 are brought into electrical engagement with a conducting strip 420 which is suitably secured in spaced relation above the insulating block 344 by means of spacing members 422 andis provided with an external connection terminal 424, as shown in Fig. 5. The size of the openings M8 in the slidable plate 354 are sufilcient to prevent electrical engagement with the said plate, irrespective of its position. An electrical terminal 426, to which external connections may be made, is secured in a suitable manner to the insulating block 344 in electrical engagement with the conducting spring strip 4I4.

With the construction just described, it will be understood that it is unnecessary for the user to hold down a signal button for more than a momentaryperiod, ,during which electrical engagement is effected in the signal circuit, and after which the button may be released and restored to its original position by means of the spring 4.

Having obtained an understanding of the construction and mechanical operation of my improved desk-type telephone set D, reference is now made to Fig. 2 of the drawings which diagrammatically illustrates a modified form of my inter-outer telephone system, in which the various branch stations, such as A and B of the inter-oflice system, are provided with such desk-type telephone sets. The operator's station 0 embodies a wall-type tof telephone set similar to that previously! described in connection with Fig. 1, and located at the operator's station 0"; as in Fig. '1,are a public telephone set T having a French style telephone instrument F and also an acoustical coupling device C.

This acoustical coupling: device C is generally similar to that previously described, except that instead of having its electronic amplifler 60 automatically connected to the source of power switch 428 and a plurality of power supply conductors 432 and 434, across which a signal lamp 430 is connected to indicate when the amplifier is being energized.

The public telephone set T" rests upon a floating platform I4 forming a part of a sub-base (not shown), but which is similar in construction and operation to that set forth in Fig. l and which includes a plurality of cooperating spring contacts 22 and 24' by means of which a signal device 26 is connected across the power conductors 432 and 434 through conductors 436 and 438 when the telephone instrument F is removed from its cradle for use.

In order to avoid confusion, it is pointed out that while for convenient reference and understanding of the operation of the system of Fig. 2, the telephone set D located at station B is shown in an operating position adapted for acoustical connection with the public telephone system, it is, nevertheless, assumed in the immediately following explanation of the system as employed for inter-office communication, that the telephone set D at station B occupies its normal operating position, which is identical to that shown with respect to the telephone set D at station A.

Therefore, with this assumption, the manner of communication between station A and the operators station is as follows: The party at station A first signals the operators station 0 by pressing push button I14 thereby operating the buzzer I18 at station 0. Thereupon, the operator removes the receiver 82 from its hook lever 84, and as soon as the party at station A picks up the telephone instrument E from its cradle 261, a telephone operating circuit is immediately established between the two stations. This circuit is from one side of battery I through conductor I80 and impedance coil I82 to a junction point I86, where the circuit. divides, one branch including conductor I88, which interconnects the two stations, the

balance of which circuit will presently be described, while the other branch includes conductor I90 to a junction point I92, where the circuit again divides, one branch including conductor I94, receiver 82 and conductor I96, while the other branch includes the transmitter 80' at station 0 and then joins conductor I86, the circuit being completed through spring contacts 94 and 92 and conductor I90 to the other side of the battery. The transmitter 80' and the receiver 82 are thus connected in multiple across the battery I10.

Referring again to the conductor I88, which interconnects the stations 0 and A, the bal-' ance of the circuit includes conductor 202 to a junction point 204, where the circuit again divides, one branch including spring contacts 11. and e of change-over switch I08 .at station A,' conductor 206', receiver I02 at station A, conductor 208, spring contacts b and a and conductor 209, and the other branch including conductor 2I0, spring contacts 7" and k of change-over switch I08 at station A, conductor 2I2', transmitter I00 at station A, conductor 2I4, spring contacts h and g, and conductor 2I6 which joins with conductor 209, the circuit being completed through conductor 2I8', spring contacts 304 and 302 of the telephone switch 300 associated with the desk set D, and conductors 220 and 200 to the other side of the battery. The circuit just recited connects the receiver I02 and the transmitter I00--at station A in multiple across the battery I10 and also in multiple with the receiver 82 and transmitter 80 at the operators station 0. Under these conditions, the system is in readiness for interoffice communication between stations 0 and A.

Upon completion of the conversation, the operator at station 0 returns the receiver 82 to ,its hook lever and the party at station A restores the telephone instrument E to its cradle, whereby the circuits just described are interrupted and the system restored to normal inoperative condition in readiness for future use.

Although I have described specifically the circuit connections for telephonic communication between the operators station 0 and the branch station A, it will be understood that the operator's station 0 may communicate with any of the branch stations, and that any branch station may communicate with the operator's station or any other branch station. However, in view of the foregoing detailed description of the circuit connections and manner of utilizing the system for inter-office communication, it is deemed unnecessary to describe the operation and circuit connections for communication between other stations of the system.

For purposes of explaining the operation of my invention when a party at one of the branch stations desires to be connected to a party on the public telephone system, it is now assumed that the party at station B wishes to make such a call and also that the desk-type telephone set D at station E occupies its normal-position, such as shown at station A, instead of the position actually shown at station B.

Under these conditions, the party at station B depresses signal button I18 to signal the operator at station 0 by means of the buzzer I'I8'.' ceiver 82' and the party at station E picks up the French telephone instrument E, an interoifice telephone operating circuit is established between stations 0 and B, which, by reason of its similarity to that just described between stations 0 and A, need not be again recited.

Having established such communication, the party at station B advises the operator of his desire to talk with some specified party on the public telephone system, whereupon the party at station B depresses the shift button I06 to actuate the change-over switch I08 to the position shown in Fig. 2 with respect to station B,

v said position being identical to that previously described and shown in Fig. '7.

The operator then hangs up the receiver 82',

and in the usual manner calls the desired party on the outside public telephone system. Of course, as soon as the French telephone instrument F is removed from its cradle by the operator, the signal lamp 26 is lighted, assuming, of course, that the power switch 428 has previously been closed, which action also supplies energy to the amplifier 60 and also operates the signal lamp 430. When the desired party has been secured, the operator places the French telephone instrument F in acoustical relation with the acoustical coupling device C, and in so doing depresses actuating rod 54 to engage the switch arm 52 with thestationary contact 50' 01 the control switch 48'. Upon the closure of the control switch 48, said switch connects a signal lamp 439 associated with the coupling device C across the power conductors 432 and 434, as will be understood.

By reason of the actuation of the change-over As soon as the operator picks up the reof the amplifier.

' at the time the shift button I08 at station B switch I08 at station B through the agency of the shift button I06, separate independently operable transmitting and receiving circuits are established between station B and the coupling device Cat station The receiving circuit includes microphone 44 and the amplifier 60, the output circuit oi which, starting from one of the output terminals 68, includes conductor 228', spring contacts 0 and b of change-over switch I08 at station B, conductor 208, receiver I02 at station B", conductor 206', spring contacts e and ,f of change-over switch I08, and conductor 232 to the other output terminal 68 The transmitting circuit is from one side of battery I4 through conductor 236, loud speaker 46 of the coupling device C, conductor 238, spring contacts 2" and h, of change-over switch I08 at station B, conductor 2I4', transmitter I00 at station B, conductor 2I2, spring contacts k and l of change-over switch I08, and conductor 242 to the other side of the battery. 4

By means of these separately operable receiving and transmitting circuits and the acoustical coupling between the French telephone instrument F and the coupling device C, telephonic communication is established between branch station B and the public telephone system, which may be employed in the usual manner.

Concurrently with the establishment of these telephone operating circuits at the time that the shift button I06 is depressed, an interlocking control circuit is established from one side of the battery 14, through conductor 242, conductor 440, slidable latching plate 354 at station B, conical head member 336, conducting rod 334, spring strip 348, terminal 350, conductor 442, electromagnet 398 of the interlocking device 396 at station A, conductor 444, electromagnet 398 of the interlocking device 396 at station B, conductor 446, electromagnet 254 or electromagnetically operated switch I0 in the coupling device C and thence by conductor 236 to the other side of the battery.

The electromagnets 398 of the interlocking devices 396 at all of the branch stations, in this instance at stations A and B, are thus energized to exert a pull upon their respective armatures 400. In view of the fact that the shift button I06 and the change-over switch I08 at station A occupy their upper operating positions, the armature 400 at station A is actuated into a locking position immediately below the cylindri cal floating member 330 of the change-over switch. This prevents the party at station A from actuating the change-over switch into its lower operating position. The armature 400 of the interlocking device 396 at station B is prevented, by the lowered position of the floating member 330 at said station, from being moved into a locking position. In this way,-the telephone desk sets at station A and any other branch stations, with the exception of station B.

are so interlocked that it is impossible for them to be utilized for establishing connections for acoustical communication with the public telephone system, so long as station B is being used for that character of service.

Before proceeding with a description of the manner of operation after the inter-outer telephone conversation is terminated, it is desirable to explain a preparatory step which took place was first depressed, as this step is important in connection with eiiecting a subsequent automatic signal to the operator when the inter-outer communication just described is terminated.

It has already been shown that at the time that the electromagnets 398 of the interlocking devices 396 at stations A and B were energized,

electromagnet 254 in the coupling device C was also energized. Thereupon, armature switch arm 256 associated with the control switch I0 is actuated to disengage the cooperating contacts 260 thereof, thus opening the energizingcircult of the buzzer 12, which circuit is also open by reason of the normal disengagement of the switch arm 52 and contact 50 of control switch 48'. This latter control switch, however, is subsequently closed by the operator in depressing the actuating rod 54 at the time that the French telephone instrument F is placed in acoustical relation with the coupling device C. Even after the control switch 48 has been so closed, the buzzer I2 is still inoperative, by reason of the fact that its energizing circuit is still openat the cooperating contacts 260 by reason of the operation of the electromagnetically operated switch 10'.

However, after the telephone conversation between station B and the public telephone system has been completed and the party at station B has restored the telephone instrument E to its cradle 261, the weight of the cradle, with the telephone instrument in position, is suflicient to depress the. supporting rod 280 to cause the roller 308 (Fig. 4) carried thereby to engage the spring contact 302 of the telephone switch 300 and thereby disengage said spring contact from its cooperating spring contact 304, thereby interrupting the telephone receiving and transmitting circuits.

At the same time, the conical cam member 360 (Figs. 4, and 8) which is also fixed to the cradie-supporting rod 280 is depressed. and by means of the roller 356, carried by the slidable latching plate 354, forces said latching plate to the left, as viewed in Fig. 8. This action automatically releases the shift button I06 and permits the spring strip 348 to restore the shiftbutton to its normal raised position, while concurrently permitting the change-over switch I08 to likewise assume its upper operating position.

Of course, as the slidable latching plate 354 disengages the conical head 3360f the shift button I06, the electrical connection between said latching plate and said conical head is interrupted. Thereupon, the electromagnets 398 of the interlocking devices 396 at stations A and B are deenergized, and the armatures 400 thereof are restored by their respective springs 406 to their normal inoperative positions.

At the moment of deenergization of the electromagnets 398, the electromagnet 254 of the electromagnetically'operated switch I0 in the acoustical coupling device C is also deenergized. Thus, the spring 258 actuates armature switch arm 256 to close the contacts 260'. Thereupon, an energizing circuit is completed through the buzzer I2 by reason of the fact that both of the control switches 48' and 10' then occupy their closed positions. The buzzer 12 therefore is operated to warn the operator that the interouter telephone communication has been ter-. minated and that the French telephoneinstrument F of the public telephone system should be restored to its. cradle. The buzzer 12 continues tooperate until this has been done, and the control switch 48' opened by the operator through the agency of the actuating rod 54.

The system is thus restored to its initial condition and is in readiness for future use.

It has already been set forth that by reason of the interlocking feature of my invention, it is impossible at any time for more than one branch station to be employed for acoustical inter-outer communication with the public telephone system. Nevertheless, it is still possible for any of the branch stations, other than the one being used, to be utilized for inter-oflice communication, by reason of the fact that the change-over switches I08 associated with these other branch stations are locked in their upper operative positions, and are therefore in readiness for interofiice use in the manner already described.

In the foregoing description and in the drawings, I have set forth my invention for illustrative purposes as embodying a multiple circuit arrangement of the transmitters and receivers at the operators station and at the several branch stations when used for inter-oflice communication, and, while I prefer this type of circuit arrangement for such service, it is entirely feasible and, in some instances, desirable that a series circuit arrangement thereof be employed.

Although I have described my invention as embodying more or less specific details of construction, arrangement and location of parts and operation, it should be understood that many modifications may be made therein without departing from the spirit and scope of my invention, and therefore only such limitations should be imposed as are indicated in the appended claims.

I claim as my invention:

1. An inter-outer system of telephone communication comprising in combination an'interofiice telephone system comprising a plurality of branch stations adapted to be connected for inter-office communication and each having a transmitter and a receiver, an acoustical coupling device having a transmitter and a loud speaker, a public telephone system having a receiver and a transmitter adapted to be placed in acoustical relation with the transmitter and loud speaker of said coupling device, and circuit-connecting means operable by the user at each of said branch stations for connecting the transmitter and receiver thereof in one type of circuit arrangement with respect to each other for inter-oflice communication and for connecting the transmitter and receiver thereof in a different type of relative circuit arrangement with the transmitter and loud speaker of said acoustical coupling device for communication, with said public telephone system.

2. An inter-outer system of telephone communication comprising in combination, an interoifice telephone system comprising a plurality of branch stations adapted to be connected for interofiice communication and each having a transmitter and a receiver, an acoustical coupling device having a transmitter and a loud speaker, a public telephone system having a receiver and a transmitter adapted to be placed in acoustical relation with the transmitter and loud speaker of said coupling device, circuit-connecting means operable at each of said branch stations for conmeeting the transmitter and receiver thereof in one type of circuit arrangement for inter-ofilce communication and for connecting the transmitter and receiver thereof in-a different type of circuit arrangement with the transmitter and loud speaker of said acoustical coupling device for communication with said public telephone system, and interlocking means disposed at each branch station and depending upon the opera tion of said circuit-connecting means at any one branch station for preventing all of the other branch stations from being connected to said acoustical coupling device for communication with the public telephone system when said one branch station is already so connected.

3. An inter-outer system of telephone communication comprising in combination an interoffice telephone system comprising a plurality of branch stations adapted to be connected for inter-ofiice communication and each having a transmitter and a receiver, an acoustical coupling device having a transmitter and a loud speaker, a public telephone system having a receiver and a transmitter adapted to be placed in acoustical relation with the transmitter and loud speaker of said coupling device, circuit-connecting means operable at each of said branch stations for connecting the transmitter and receiver thereof in one type of circuit arrangement for inter-office communication and for connecting the transmitter and receiver thereof in a different type of circuit arrangement with the transmitter and loud speaker of said acoustical coupling device for communication with said public telephone system, and interlocking means disposed at each branch station and depending upon the operation of said circuit-connecting means at any one branch station for preventing all of the other branch stations from being connected to said acoustical coupling device for communication with the public telephone system when said one branch station is already so connected, and for permitting concurrent inter-oflice communication between any two of said other branch stations while said one branch station is connected to said coupling device.

4. An inter-outer system of telephone communication comprising in combination, a multi- -station inter-oillce telephone system having a receiver and transmitter at each branch station, means at each branch station operable by the user thereof for connecting the receiver and transmitter at said station in multiple circuit arrangement with each other for inter-office communication, a, public telephone system having a French type telephone instrument, acoustical coupling means including a transmitter and a loud speaker for coupling said transmitter and loud speaker to said public telephone instrument, and means at each branch station operable by the user thereof for connecting the transmitter at said branch station and the loud speaker of said acoustical coupling means in a telephone transmitting circuit and for connecting the receiver at said branch station and the transmitter of said acoustical coupling means in an independently operable telephone receiving circuit, for acoustical communication between said branch station and said public telephone system.

5. An inter-outer system of telephone communication comprising in combination, a multistation inter-office telephone system having a receiver and transmitter at each branch station, means at each branch station for connecting the receiver and transmitter at said station in multiple circuit for inter-ofllce communication, a public telephone system having a French type telephone instrument, acoustical coupling means including a transmitter and a loud speaker for coupling said transmitter and loud speaker to said public telephone instrument, manually operable means at each branch station for connecting the transmitter at said branch station and the loud speaker of said acoustical coupling means in a telephone transmitting circuit and for connecting the receiver at said branch station and the transmitter of said acoustical coupling means in an independently operabletelephone receiving circuit, for acoustical communication between said branch station and said public telephone system, and automatically operated means located at each branch station and rendered operative when any branch station is connected with said acoustical coupling means for preventing the connection of all of the other branch stations for such use, until the connection of said branch station with said coupling means is discontinued.

6. An inter-outer system of telephone communication comprising in combination, a public telephone system including a telephone set having a removable telephone instrument, an interoflice telephone system electrically independent thereof and comprising a plurality of branch stations, each having a transmitter and a receiver, an acoustical coupling device located at the operators station of said inter-office system for acoustically connecting the telephone instrument of said public telephone system to said inter-office telephone system and including an electronic amplifier, an auxiliary transmitter and a loud speaker, and means located at each of said branch stations for connecting the transmitter and receiver at said station in multiple circuit arrangement for inter-ofllce communication, and for connecting the receiver at the branch stationhnd the transmitter and electronic amplifier of said acoustical coupling device in a receiving circuit and for connecting the transmitter at said branch station and the loud speaker of said acoustical coupling device in an independently operable transmitting circuit, when said branch station of said interoflice system is connected acoustically to said public telephone system.

7. An inter-outer system of telephone communication comprising in combination, a public telephone system including a telephone set having a removable telephone instrument, an inter-office telephone system electrically independent-thereof and comprising a plurality of branch stations, each having a transmitter and a receiver, means disposed at each of the branch stations and operable when the receiver thereof is picked up for use to automatically connect the telephone receiver and transmitter at such station in multiple circuit for inter-oflice communication, an acoustical coupling device located at the operators station of said inter-ofllce system and including an auxiliary transmitter and a loud speaker for acoustically coupling the public telephone instrument to said inter-oflice system, and manually operable means disposed at each branch system for establishing independently operable receiving and transmitting circuits between said branch station and the acoustical coupling device when any branch station is acoustically connected to the public telephone system, said receiving circuit including the receiver at said branch station and the transmitter of said coupling device, and said transmitting circuit including the transmitter at said branch station and the loud speaker of said coupling device.

8. A telephone set for inter-outer telephone systems comprising a transmitter, a receiver and manual means operable by the user of said telephone set i'or connecting said transmitter and receiver in two substantially different circuit arrangements with respect toeach other.

9. A telephone set for inter-outer telephone systemscomprising a transmitter, a receiver, and manual means operable by the user of said telephone set for connecting said transmitter and receiver either in multiple circuit or in separate and independent circuit arrangements with respect to each other.

10. A' telephone set for inter-outer telephone systems comprisinga transmitter, a receiver and a change-over switch adapted to occupy two operating positions for respectively connecting said transmitter and receiver in one circuit arrangement' with respect to each other and for connecting them in a substantially difierent circuit arrangement with respect to each other, and manual means operable by the user of said telephone set for actuating said change-over switch into either of its operating positions.

11. A telephone set for inter-outer telephone systems comprising a transmitter, a receiver and manual means operable by the user of said telephone set for connecting said transmitter and receiver in two substantially different circuit arrangements with respect to each other, means for supporting the receiver when not in use, and means associated with said receiver and cooperating with said supporting means for causing said manually operable means to connect said transmitter and receiver in a predetermined one of said circuit arrangements whenever said receiver is placed upon said supporting means and out of use.

12. A telephone set for inter-outer telephone systems comprising a transmitter, a receiver and a change-over switch adapted to occupy two operating positions for respectively connecting said transmitter and receiver in one circuit arrange ment and for connecting them in a substantially different circuit arrangement, manually operable means for actuating said change-over switch into either of its operating positions, means for supporting said receiver when not in use, and means for insuring that said change-over switch occupies a predetermined operating position when said receiver is out of use and supported by said supporting means.

13. A telephone set for inter-outer telephone 5 systems comprising a transmitter, a receiver and a change-over switch adapted to occupy two operating positions for respectively connecting said transmitter and receiver in one circuit arrangement and for connecting them in a substantially different circuit arrangement, a manually operable shift lever for actuating said change-over switch into either of its operatingpositions, a hook lever upon which said receiver is hung when not in use, and means for preventing the'receiver being hung upon said hook lever except when said shift lever and change-over switch occupy predetermined positions. s

14. A telephone set for inter-outer telephone systems comprising a transmitter, a receiver and a change-over switch adapted to occupy two operating positions for respectively connecting said transmitter and receiver in one circuit arrangement and for connecting them in a substantially different circuit arrangement, a manually operable shift button for actuating said change-over switch into either of its operating positions, supporting means upon which said transmitter and receiver rest when not in use, and means for causing said shift button and said change-over switch to occupy a predetermined operating position when the transmitter and receiver rest upon said supporting means.

15. A telephone set for inter-outer telephone systems comprising a transmitter, a receiver and manually operable means for connecting said transmitter and receiver in two substantially different circuit arrangements, and electromagnetic means for'positively locking said manually operable connecting means under predetermined conditions.

16. A telephone set for inter-outer telephone systems comprising a transmitter, a receiver and a change-over switch adapted to occupy two operating positions for respectively connecting said transmitter and receiver in one circuit arrangement and for connecting them in a substantially different circuit arrangement, manuallyoperable means for actuating said change-over switch into either of its operating positions, and electromagnetic means for positively preventing the operation of said change-over switch under predetermined conditions.

17. A telephone set for inter-outer telephone systems comprising a casing, a yieldingly mounted cradle, a, French type telephone instrument adapted to normally rest thereon, a switching device adapted tooccupy two operating positions, a manually operable push-button for actuating said switching device, and means rendered operative when said telephone instrument is placed in its cradle for causing said push-button and said switching device to occupy predetermined operating positions.

18. A telephone set for inter-outer telephone systems comprising a casing, a yieldingly mounted cradle, a French type telephone instrument adapted to normally rest thereon, a change-over switch adapted to occupy a normal position to establish certain circuit connections for said telephone instrument and another operating position to establish certain other circuit connections therefor, a manually operable shift button for actuating said change-over switch from its normal operating position to its other operating position, means for latching said shift button and said change-over switch in said other operating position, and means rendered operative when the telephone instrument is placed in its cradle for automatically releasing said latching means to permit said shift button and said change-over switch to be restored to their normal positions.

19. A telephone set for inter-outer telephone systems comprising a casing, a yieldingly mounted cradle, a French type telephone instrument adapted to normally rest thereon, a change-over switch adapted to occupy a normal position to establish certain circuit connections for said telephone instrument and another operating position to establish certain other circuit connections therefor, a manually operable shift button biased to its normal position for actuating said changeover switch from its'normal operating position to its other operating position, a movable latching member yieldingly biased to its latching position for latching said shift button and said changeover switch in said other operating position, and means mechanically associated with said yieldingly mounted cradle for actuating said latching member to release said shift button and said change-over switch when said telephone instrument is placed in its cradle, whereby said shift button and said change-over switch are automatically restored to their normal positions.

20. A telephone set for inter-outer telephone systems comprising a casing, a yieldingly mounted cradle, a French type telephone instrument.

adapted to normally rest thereon, a change-over switch comprising two groups of oppositely disposed spring contacts adapted to occupy one operating position for establishing certain circuit connections of said telephone instrument and another operating position for establishing certain other circuit connections therefor, a member of insulating material mechanically associating certain spring contacts of both groups, manually operable means adapted to be moved into engagement with said insulating member and to thereby actuate both groups of spring contacts of said change-over switch into said other operating position, and releasable means for automatically latching said manually operable means and said change-over switch in said other operating posi tion.

21. An inter-outer system of telephone communication comprising in combination an interoffice telephone system comprising a plurality of branch stations adapted to be connected for inter-oflice communication and each having a transmitter and a receiver, an acoustical coupling device having a transmitter and a loud speaker, a public telephone system having a receiver and a transmitter adapted to be placed in acoustical relation with the transmitter and loud speaker of said coupling device, and circuit-connecting means operable at each of said branch stations for connecting the transmitter and receiver thereof in one type of circuit arrangement for interoffice communication and for connecting the transmitter and receiver thereof in a different type of circuit arrangement with the transmitter and loud speaker of said acoustical coupling device for communication with said public telephone system, electromagnetic locking means disposed at each branch station in operative relation with the circuit-connecting means at said branch station and adapted when actuated to positively lock said circuit-connecting means and prevent its actuation, and an electrical circuit interlocked with the circuit-connecting means at each of said branch stations and operatively associated with the electromagnetic locking means at each branch station for energizing and causing the actuation of the electromagnetic locking means at all of the other branch stations when the circuit-connecting means at one of said branch stations is manually actuated into position to establish telephone circuits between said branch station and the acoustical coupling device.

22. A telephone set for inter-outer telephone systems comprising a transmitter, a receiver and a change-overswitch adapted to occupy two operating positions for respectively connecting said transmitter and said receiver in one circuit arrangement in one of its positions and in a substantially different circuit arrangement in its other position, manually operable mechanical means for actuating said change-over switch into either, of its operating positions, means for supporting said receiver when not in use, and mechanical means cooperating with said receiver supporting means and said mechanical actuating means when said receiver is placed upon said supporting means for necessitating that the changeover switch be actuated to a predetermined one of its operating positions to connect the telephone receiver and transmitter in a predetermined one of the two circuit arrangements.

23. A telephone set for inter-outer telephone systems comprising a transmitter, a receiver and a change-over switch adapted to occupy two operating positions for respectively connecting said transmitter and receiver in one circuit arrangement and for connecting them in a substantially dlfi'erent circuit arrangement, manually operable means for actuating said change-over switch into either of its operating positions, and electromagnetic means for positively locking said manually operable actuating means against movement under predetermined conditions.

24. A telephone set for inter-outer telephone systems comprising a casing, a yieldingly mounted cradle, a French type telephone instrument adapted to normally rest thereon, a change-over switch comprising two groups of oppositely disposed spring contacts adapted to occupy one operating position for establishing certain circuit connections of said telephone instrument and another operating position for establishing certain other circuit connections therefor, manually operable means interposed between said two groups of spring contacts and adapted to occupy two operating positions to actuate the two groups of spring contacts into one or the other of their operating positions, releasable means for automatically latching said two groups ofspring contacts of said change-over switch in one of its operating positions and means dependent upon placing the telephone instrument upon its cradle for releasing said releasable latching means.

25. A telephone set for inter-outer telephone systems comprising a casing, a yieldingly mounted cradle mounted thereon, a telephone instru- Inent adapted to normally rest upon said cradle, a plurality of selective signal buttons biased to their raised positions but adapted when manually depressed to establish signal circuits, a changeover switch disposed within said casing for establishing'the circuit connections of said telephone instrument, a manually operable shift button biased to its raised position but adapted when depressed to actuate said change-over switch, means for automatically latching said shift button in its depressed position and means for releasing said latching means when the telephone instrument is replaced upon its cradle.

RICHARD VARLEYL 

